This is driving me insane! I went to the brush options and turned on
Back face masking, I tried every setting (Don’t seem to do anything at all),
I turned off symmetry, I inflated the mesh in case it had zero density, I
searched online and there is NOTHING I have no way to only mask one side of a mesh!
It always masks both sides!
Please help, I’ve been stuck here for hours 
It would be helpful to see your mesh to better understand the situation. But you can always separate the front and back sides into separate polygroups, after which you can hide one or the other by shift-ctrl clicking them, mask it by ctrl-clicking in empty canvas, then inverting the mask by ctrl clicking in empty canvas again when everything is visible.
Note the “Group Front Facing polygons” function in the Tool> Polygroups menu. If your object is relatively low poly and planar, you can use the ZMod brush to either mask or polygroup entire sides at a time.
You really need to understand the information on the following pages to be able to quickly and easily work with meshes in Zbrush:
http://docs.pixologic.com/user-guide/3d-modeling/modeling-basics/polygroups/
http://docs.pixologic.com/reference-guide/tool/polymesh/polygroups/
http://docs.pixologic.com/user-guide/3d-modeling/modeling-basics/mesh-visibility/
http://docs.pixologic.com/user-guide/3d-modeling/modeling-basics/masking/
http://docs.pixologic.com/reference-guide/brush/auto-masking/
Thanks for the reply,
this is my problem right now:
When I hit ctrl and paint in the front of the skirt, I get this inside.
The only thing I want is to be able to mask the top without it masking
inside. I know it can be done because I’ve seen people do it, but no matter
what I try nothing works.
Even if I use polygroups and it works I will never be able to find out what I’m
doing wrong with masking… 
You’re not necessarily doing anything wrong. There’s always been a bit of bleed through when masking with large brush falloffs on thin volumes. At least, there was in zbr6. Backface mask works much better when you’re actually sculpting or painting, than it does for masking.
Keep in mind there are other options for auto masking in the brush >automasking menu, like topological masking, that may be of help.
It would be best, however, to become very comfortable with polygroups and the associated visibility shortcuts. It will make issues like this seem trivial.
You should be able to group most of the interior and exterior of that dress into polygroups with the Tool > Polygroups> Group by normals function.
Wow after 3 hours of sitting here pulling my hair, this is the right answer!
I made my brush the size of a pencil and it didn’t bleed trough, this is super
annoying but at least now I know the reason. Thanks so much for this!
So If I want to shape thin objects and make them move like cloth I have to
use poly groups because masking will always bleed trough? Like if I want to make
the skirt cut into large strips and shape it so it looks waving in the air?
Thanks again!
No, not neccesarily. Like I said automasking works much better when you’re actually painting or sculpting. It is, after all, a function designed to replace the *need" for masking.
Try simply painting or sculpting on the forward surface of the dress with backface masking active without masking. You should find you’re able to influence only the one side with very few or any effects on the reverse side. There are always exceptions with cases of extreme geometry.
The reason I was trying to use masking was to make an extrusion
because the skirt is not one piece, it’s cut into pieces and I would have
to either extrude these tails or somehow cut in between and for both
I would need to mask it. To see the skirt there’s a picture in my Gallery.
My other option is to make each tail separately…
I see your problem, yes. As I said originally, the answer to your problem is polygroups.
If the dress object was originally created with a subtool extract, then it should already have the inner and outer surface separated into polygroups. Switch on polyframe mode to view polygrouping.
Simply shift-ctrl click on the outer polygroup to hide all but that polygroup, then paint your masking. If you want to be able to see the rest of the model while you’re working, simply shift-ctrl click on the inner surface, then do it again to make everything except that problematic inner surface visible. Paint your masking without worrying about the inner dress, shift-ctrl click in empty canvas to unhide everything, then perform your extraction.
If you don’t have polygroups, the Tool> Polygroups> “Group by normals” function should split the outer and inner dress into separate polygroups without much tweaking.
You can also create those dress extensions with the Topology brush.
Please read over the articles I linked above, and commit those shortcuts to muscle memory. It will vastly improve your ability to quickly and easily do what you want in zbrush.
Ok Thanks a lot! I’m learning more about Polygroups and
tomorrow Ill memorize the shortcuts and continue with the skirt.
Is it ok if I PM you if I get into more trouble? ^^
Goodnight ^^
It would be best that questions were asked in the forums so that the answers might benefit anyone else with a similar problem.
Ooookkk… I’m not sure to have understood you.
But maybe yes. (Sorry first for my english).
Ok. A solution:
1.) mask first all that what you want have masked. Also if the inside will masked with.
2.) Then go to the Brush Menu and search:
The -Automasking- submenu. And there click now the button -BackfaceMask- (after you have masked everthing) - BUUT:
Hold CTRL(= Masking on!) before you click the -BackfaceMask- button; Because otherwise you have not really activated the -BackfaceMask- during you paint with masking (Ctrl for mask painting):
3.) Now you clear mask areas with “painting”, holding the Alt-Key together with the Ctrl-Key on your keyboard.
But with set [Freehand] for “paint” masking areas away.
PS. 4.) If you have finally painted well away, with the Alt-Key that mask areas that you not want have more, then you can go to -Polygroups- Submenu (Tool Mainmenu) and there you click then [Group Masked]-(but first set the slider -Polish- there to 1).
That will polish your new polygroup which you have now created with the visible masked areas, when you click [Group Masked].
;o)
@Designitalive
omg your a genius! it worked perfectly!! XD
I need to write this down in sticky notes or something
lol.
The reason I haven’t use Polygroups much is because every time
I do Dynamesh I loose them. There’s noway around this is there?
Ill try to shape the skirt now with polygroups ^^
Good call, DesignitLive! It didn’t even occur to me you might not have backface masking activated for your masking brush.
Re: Polygroups and Dynamesh. Dynamesh should keep a rough approximation of your polygrouping, but you can easily re-establish it again with the polygroups> group by normals button.
Ah ok, Group by normals kinda works but it also makes a couple of other random
poly groups. This is what I have so far:
It took me several hours just to get this much U_U
but now’s the big problem, how do I shape them to look
like moving cloth? I’m using the move tool but it’s almost
impossible…
Or did I have to model them like that directly and is not possible
to pose them now?
If you draw them out with the topology brush, you should be able to create them as low poly geometry that would be easier to pose. Likewise you can run those through ZRemesher to create lower poly versions that might be easier to move verts around with.
Otherwise, if you were going to extract them, it might be better to extract them from a solid shape you had already sculpted into more or less the correct form.
The trick to using the Move brush is to adjust your brush size and falloff. It may be helpful to switch off dynamic size mode of the brush, so you can get really large falloffs. That way your move will be applied more evenly to the whole cloth, and not a small part of it.
If I were doing this, I’d create the extensions as low poly single plane geometry with the topology brush and a thickness of zero. I would then move the points around where I wanted them, then give them some thickness with QMesh, subdivide them up, and sculpt more detail into them.
http://docs.pixologic.com/user-guide/3d-modeling/topology/topology-brush/
@Designitalive
omg your a genius! it worked perfectly!! XD
I need to write this down in sticky notes or something
lol.
The reason I haven’t use Polygroups much is because every time
I do Dynamesh I loose them. There’s noway around this is there?
Ill try to shape the skirt now with polygroups ^^
Or better:
You make a screenshot of the Browser with the Hotkeys:
[FN] (hold) and then one click to [Insert Prt Sc]-the keyon the leftside of the delete keyboard key .
And then you open PS or Windows Paint Programman click: Ctrl + V.
But this works only on PC. On MAC i don’t know how to make a Screenshot.
And then you cut/slice this image in the size where only is to see the text of my tutorial ;o)
I’m not sure to understand you (because my english is really not great).
But you can also hold the polygroups in DynaMesh Modus. Click before you go in DynameshModus:
the [Group] Button. I think that will safe your Polygroups.
@Spyndel Yeah, but that’s the point. I also forget that often; to hold Ctrl before i click Backface lol